light

light

[līt]

electromagnetic radiation with a range of wavelength between 390 (violet) and 770 (red) nanometers, capable of stimulating the subjective sensation of sight; sometimes considered to include ultraviolet and infrared radiation as well.

idioretinal light (intrinsic light) the sensation of light in the complete absence of external stimuli.

polarized light light of which the vibrations are made over one plane or in circles or ellipses.

Wood's lightultraviolet radiation from a mercury vapor source, transmitted through a nickel-oxide filter (Wood's filter or glass), which holds back all but a few violet rays and passes ultraviolet rays of wavelength around 365 nm; used in diagnosis of fungal infections of the scalp and erythrasma, and to reveal the presence of porphyrins and fluorescent minerals.

light

(līt),

1. That portion of electromagnetic radiation (for example, 390-770 nm) to which the retina is sensitive (wavelength range, 380-780 nm). See also: lamp. See also: lamp.

light

photophobia.

light

(līt) electromagnetic radiation with a range of wavelength between 3900 (violet) and 7700 (red) angstroms, capable of stimulating the subjective sensation of sight; sometimes considered to include ultraviolet and infrared radiation as well.

idioretinal light the sensation of light in the complete absence of external stimuli.

intrinsic light the dim light always present in the visual field.

polarized light light of which the vibrations are made over one plane or in circles or ellipses.

Wood's light ultraviolet radiation from a mercury vapor source, transmitted through a nickel-oxide filter (Wood's filter, or glass), which holds back all but a few violet rays and passes ultraviolet wavelengths of about 365 nm.

light

Etymology: AS, leoht

1 electromagnetic radiation of the wavelength and frequency that stimulate visual receptor cells in the retina to produce nerve impulses that are perceived as vision.

2 electromagnetic radiation with wavelengths shorter than ultraviolet light and longer than infrared light, the range of visible light generally in the range of 400 to 800 nm.

light

light

That portion of electromagnetic radiation to which the retina is sensitive. See also: lamp

[A.S. leōht]

light

that part of the ELECTROMAGNETIC SPECTRUM which is visible to the human eye between about 400 nm (blue) and 770 nm (red).

light

visible electromagnetic radiation

light

Electromagnetic vibration capable of stimulating the receptors of the retina and of producing a visual sensation. The radiations that give rise to the sensation of vision are comprised within the wavelength band 380-780 nm. This band is called the visible spectrum or visible light. The borders of this band are not precise but beyond these radiations the visual efficacy of any wavelength becomes very low indeed (less than 10−25). Seecoherent sources; infrared; absorptive lens; spectroscope; electromagnetic spectrum; visible spectrum; Table C4; quantum theory; wave theory; ultraviolet; wavelength.achromatic lightSeeachromatic light stimulus.light adaptationSeelight adaptation.artificial light Any light other than natural light.beam of light A collection of pencils arising from an extended source or object. Syn. bundle of light. Seepencil of light.bundle of lightSeebeam of light.light chaosSeeidioretinal light.cold light Any visible light emitted by a process other than incandescence such as lasers, glow worms, certain chemical reactions, etc. Cold light is free of infrared.compound light Light composed of more than one wavelength.diffuse light Light coming from an extended source and having no predominant directional component. Illumination is thus relatively uniform with a minimum of shadows. Seediffusion; extended source.fluorescent light Light emitted by fluorescence as in a fluorescent lamp. Electricity excites a gas that produces ultraviolet light, which in turn causes a phosphor coating on the inner surface of the fluorescent tube to fluoresce and emit visible light. Examples: mercury vapour lamp, neon and argon lamps, sodium vapour lamp, xenon flash lamp.frequency of lightSeehertz; electromagnetic spectrum; wavelength.idioretinal light A visual sensation occurring in total darkness that is attributed to spontaneous nervous impulses in the neurons of the visual pathway. Syn. intrinsic light; light chaos.incandescent light Light emitted by incandescence as in an incandescent lamp. An electrical current passes through a thin filament (e.g. tungsten) enclosed in a sealed oxygen-free glass bulb. The filament is heated and photons are released. Seefilament lamp; halogen lamp.infrared lightSeeinfrared.intrinsic lightSeeidioretinal light.monochromatic light Light consisting of a single wavelength or, more usually, of a narrow band of wavelengths (a few nanometres).natural light Light received from the sun and the sky.pencil of light A narrow cone of light rays coming from a point source or from any one point on a broad source after passing through a limiting aperture. A pencil of light may be convergent, divergent or parallel. The ray passing through the centre of the aperture is the chief ray. Syn. homocentric bundle of rays; homocentric pencil of rays. Seebeam of light.polarized light Ordinary light is composed of transverse wave motions uniform in all directions in a plane perpendicular to its direction of propagation. Polarized light is composed of transverse wave motions in only one direction, called the plane of vibration. Polarized light can be obtained by using a polarizer (e.g. tourmaline crystals, polarizing material such as Polaroid, Nicol prism, etc.). Seeanalyser; angle of polarization; dichroic crystal; polarizing lens; polarizer; Wollaston prism; vectogram.quantity of light Product of luminous flux and its duration. Unit: lumen-second. Seelumen.light reflexSeecorneal reflex; pupil light reflex.solar light Light from the sun or having identical properties as the sun. Seeeclipse blindness; white light.light source Any source of visible radiant energy such as natural light (e.g. daylight, moonlight, sunlight) or artificial light (e.g. a candle flame, an incandescent lamp, a discharge lamp, a fluorescent lamp). Seecoherent sources; CIE standard illuminants.speed of light The currently accepted figure is 299 792.5 km/s (in a vacuum). This velocity decreases, differentially with wavelength, when the radiation enters a medium. Seeindex of refraction; electromagnetic spectrum.light stopSeediaphragm.stray light Light reflected or passing through an optical system but not involved in the formation of the image such as that reflected by the surfaces of a correcting lens. Syn. parasitic light. Seeghost image.light thresholdSeelight absolute threshold.ultraviolet lightSeeultraviolet; Wood's light.visible lightSee light; visible spectrum.white light Light perceived without any attribute of hue. Any light produced by a source having an equal energy spectrum will appear white after the eye is adapted. Some of the CIE illuminants are often used as a source of white light, e.g. B, C and D. Sunlight is a source of white light. Seechromaticity diagram; equal energy spectrum.Wood's light Ultraviolet light near the visible spectrum which, when used with certain dyes such as fluorescein, causes fluorescence. It is produced by a special type of glass (called Wood's glass or Wood's filter), which contains nickel oxide and transmits ultraviolet radiations near the visible spectrum. It is used to detect corneal abrasions and to evaluate the fit of hard contact lenses. It is available in a slit-lamp or in a Burton lamp. Seefluorescein; fluorescence; Burton lamp.

light

(līt)

That portion of electromagnetic radiation to which the retina is sensitive. See also: lamp

[A.S. leōht]

light,

n1. the electromagnetic radiation of the wavelength and frequency that stimulate visual receptor cells in the retina to produce nerve impulses that are perceived as vision. 2. visible light ranges from 400 to 800 nm.

light

electromagnetic radiation with a range of wavelength between about 390 nm (violet) and 770 nm (red), capable of stimulating the subjective sensation of sight; sometimes considered to include ultraviolet and infrared radiation as well.

light beam diaphragm

adjustable lead shutters at the aperture of an x-ray tube. Usually includes a light bulb which delimits the area covered by the beam at the cassette level.

light cattle

store class cattle off range and destined for movement onto irrigated pasture or into feedlot for fattening.

light-dark cycles

an important environmental factor in proper housing of laboratory animals for optimal health and reproductive cycling. Most species do well on a 12:12 light-dark cycle but in rabbits more light for females and less for males is recommended.

polarized light

light of which the vibrations are made over one plane or in circles or ellipses.

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